This invention relates to a fuel delivery rail assembly for an internal combustion engine, especially for an automotive engine, equipped with a fuel injection system. The fuel delivery rail assembly delivers pressurized fuel supplied from a fuel pump toward intake passages or chambers via associated fuel injectors. The assembly is used to simplify installation of the fuel injectors and the fuel supply passages on the engine.
An example of an automotive engine cylinder head equipped with a fuel injector is shown in FIG. 5 of the attached drawings. In this cylinder head, toward inside of an intake manifold 52 leading to a cylinder 51, pressurized fuel is discharged from a fuel injector 55. The fuel delivery rail assembly 60, which concerns a substantial matter of the present invention, is only partially shown as a section of a socket 61. In this type of fuel delivery rail assembly, the injector 55 is accommodated within the socket 61 and fixed thereto by a cap 66 having an electrical terminal. Between the injector 55 and the socket 61, two 0-rings 58 and 59 are located in order to keep fluid tight seals therebetween.
A complete form of the fuel delivery rail assembly 60 is shown in FIG. 6. In this assembly 60, three tubular sockets 61 are interconnected by connecting pipes 62. Each of the sockets 61 is located at a predetermined distance from each other. These metallic sockets 61 are initially made through a forging process, and then directed to a precise machining work. In this step, especially interior surfaces of the socket should be smoothly finished in order to establish a fluid tight seal of O-ring. For this purpose, a special machining process of burnishing work is commonly utilized to effect a high grade of circumferential accuracy as well as surface smoothness.
Each socket 61 comprises a tubular body 63 having a top opening, a bottom opening and two lateral openings facing opposite directions. These lateral openings are used to receive distal ends of the connecting pipes. By means of brazing connections 64, the sockets 61 and the pipes 62 are fixed together. On upper flange of the tubular body 63 of the socket 61, a pair of extensions 65 having threaded holes are provided so as to receive the cap 66 (see FIG. 5) and to be bolted together.
Since the conventional fuel delivery rail assembly is constructed as stated above, many kinds of workings are necessary for manufacturing of the assembly. In particular, the interior surfaces of the socket 61 should be finished extremely smooth in order to establish a complete fluid seal between the surface and the resilient seal members and also to avoid breakdown of the seal members, because they are mounted on the injector 55 when it is inserted into the socket 61. The following steps are needed in manufacturing of the socket 61. At first a rough fabrication is made by a forging work, and then it is machined to make a form of the interior surface. Finally, the socket is finished with a burnishing machine until the predetermined smoothness is obtained. Under the situation, for manufacturing of the socket 61, many kinds of time-consuming working steps and transferring handlings are needed, resulting in an increase of manufacturing cost.